As most people are aware, many locks are automatically actuated when a door is closed so that the door cannot be reopened from the outside without a key. However, a large number of locks are used, for example as deadbolts, which must be acutated from the outside with a key to lock and unlock the door.
With today's rapidly increasing crime rates, people must take additional steps to ensure not only their own safety, but also the security of their possessions from crimes such as robbery and burglary. As a result, many home owners and business people are adding additional locks to their doors, usually in the form of deadbolts which are normally more secure than the standard door knob lock.
On many occassions, when someone leaves a building, in order to ensure the necessary safety of the possessions left in the building, as well as the security of the next person to reenter, it is important that key actuated locks, such as deadbolts, security alarms, etc., be actuated. On the other hand, pressure to get to the next place of activity, forgetfulness, etc., often cause people either to forget to actuate the locks or to be unable to remember later whether or not they did actuate the locks. It often happens, for example, that someone will travel a distance from the building which was to be secured, suddenly remember that he should have secured it, but be unable to remember whether or not he actually did.
In such instances, it would be extremely helpful to such people to have a memory aid so that they would be able to instantly determine whether or not they had actuated the locks. Without such an aid, the individuals concerned must either take a chance about the security, hoping for the best, or return to the building, wasting time and energy.
Accordingly, a need has long existed to provide a very convenient, unforgetable memory aid which will immediately reveal whether or not a lock was actuated. In the past, various inventors have come up with memory aids which, had they been practical, would have provided such a clear indication. Those inventors came up with devices which could be attached to the key used to actuate the lock and provide an indication as to whether or not the key had been used as required. An early device of this type is shown in U.S. Pat. No. 1,237,155 which depicts a key and a lock having an indicator system which would be actuated when the key was turned in the lock. However, that device was only theoretically useful since it was so intricate and complex as to be impractical. The head or handle of the key had to be provided with moving levers which were actuated by a cam on the face of the lock itself, thus requiring not only a special lock, but also a very expensive key.
U.S. Pat. Nos. 1,843,335 and 2,418,046 each depict a key which has to be slotted and provided with special hardware, including springs, cams, etc., which are actuated when the key is turned. In the case of the earlier of these patents, the lock has to be modified to allow entry of a cam into the lock for cooperation with a fixed pin for movement of the cam to provide the desired indication. In a later patent, the cam is actuated by contact with the face of the lock itself. These devices were both impractical because of the intricate and delicate nature of the structures involved and they further required that the lock either have a special face or a flat face which could cooperate with the cams to provide the desired indications.
U.S. Pat. No. 2,561,944 discloses the use of a casing which snaps onto the head or handle of a key. The casing is provided with a spring-biased indicator which is pushed against the lock face when the key is inserted. Rotational movement of the key causes the indicator to pivot to expose an indicator symbol, again requiring that the lock have a flat face with which the indicator comes into contact to cause the pivoting. Further the structure requires small and intricate parts including springs, etc., which are difficult and expensive to assemble and maintain in proper operation.
U.S. Pat. No. 2,373,893, also discloses a device which requires that the lock be provided with a special face and that the key be intricately and delicately machined and provided with moving parts. This device is very expensive and difficult to produce and maintain.
U.S. Pat. Nos. 2,176,464 and 2,198,484 both disclose keys which provide an actuation indication, but which have to be produced in multiple sections with relatively intricated machining, requiring expensive assembly, etc.
Further, most of the above-described inventions are deficient because they require special keys, thus preventing the user from employing the different indicator systems with nearly any key he might have in his pocket. Also, in almost every instance, the inventions were disclosed on the assumption by the inventors that all locks work in a single direction, i.e., clockwise rotation of every lock will lock it and counterclockwise rotation of every lock will unlock it. Obviously, this is not true since locks must be able to work in different directions for different applications. In most cases, the position of the particular structure relative to the juncture of the handle and shank is relatively critical since the lock face must be used to actuate the indicator.
Consequently, a need still exists for a very simple, inexpensive device which can be employed with nearly any standard key to provide an indication to the user as to whether he last actuated a lock to lock it or unlock it.